With the Bat family getting made this year to celebrate the 75th Anniversay of the Dark Knight it's noticeable that Batwoman hasn't been done by DCC. Williams art helped Batwoman stand out and it seems like a no brainer to get a line with Kate, her family and rogues gallery.
Whether you like the new Wonder Woman or not I think a lot of fans would still want some figures based on the amazing art. Besides Diana is one of the Trinity which means she should have her own line. Given the characters involved this could potentially go on for awhile.
Aquaman may not have the popularity of Batman or Superman but he has gotten more attention since the relaunch. The costumes aren't that different for pre-52 either. Given the high profile of Reis it seems like a style a lot of fans would love to see.
I haven't been reading this, I'm more of a GLC fan, but I love the work Mahnke does. Plus it's been proven that any GL line sells and there's plenty to make. And hey other characters showed up too.
He's done RHATO, Superman and is now on TT. I think his line could cover all three. We might even get some characters we wouldn't get otherwise like Essence.
Other mentions: I'd like Aaron Lopresti and Dan Jurgens too but I don't think their as likely since to the best of my knowledge their not currently working on any projects. Well Jurgens is writing but I don't think he's doing the interior art for the Booster Gold one shot. There are other artists for this list too but I don't think their as likely for the same reasons. Still I might have missed some, is there anyone else you think deserves to their own line?